<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>弹性布局引例</title>
  <link rel="stylesheet" href="style.css">
</head>

<body>
  <div id="flex_wrap">
    <div class="flex_box" id="red_box">弹性盒子1</div>
    <div class="flex_box" id="green_box">弹性盒子2</div>
    <div class="flex_box" id="blue_box">弹性盒子3</div>
  </div>
</body>

</html>